Color stability of composite resins performed by two instrumental methods

Objectives: The aim of this study is to evaluate the color stability of composite resins, immersed in different liquides.

Methods: 64 composite disks (30/2 mm) were prepared using a teflon matrix. The composite specimens were distributed as follows (n=16): group 1 Premise (Kerr Hawe), group 2 Gradia Direct (GC), group 3 experimental composite Napoglass, group 4 experimental composite Radopacril, all B1 shade. The L*_, a*, b* values were measured from the composites specimens using two methods: UV-VIS UNICAM spectrophotometer; and the computer analisys of digital images (CADI) (images were taked using a digital camera, and analyzed with Detcolordent 1.0 software). Each group was divided in 4 subgroups, 4 specimens/subgroup. Subgroup 1 was immersed in artificial saliva at 37^oC (AS), subgroup 2 in coffee (CA), subgroup 3 in beverage A (BA), subgroup 4 in beverage B (BB). The composites specimens in subgroup in 2, 3, and 4 were immersed 3 hours per day in the colorant solution and the rest 21 hours in artificial saliva at 37^oC. The protocol was carried out for 21 days. The color parameters of the composite specimens was measured using the two methods and a second set of L*_, a*, b* values was obtained. The ΔE* was calculated. The results were statistically analyzed using the SSPS 13.0 for Windows – Wilcoxon test.

Results: The ΔE* values obtained were situated in the interval 0.37-14.24 for the spectrophotometrical analysis and 1.35-11.05 for CADI. The higher ΔE* values were obtained for the samples immersed in CA, and the lowers for samples immersed in AS and BB, for all groups, and with the bought  measuring methods.

Conclusions: The results obtained with the two measuring methods were similar. The highest color changes were produced by coffee, the lowest by artificial saliva. Napoglass presented the highest color changes from all the composites.